Tennessee Wastewater Operator Practice Exam

Why should solids be removed from the digester immediately before feeding the digester?

1. To improve biogas quality

2. To prevent short circuiting

3. To reduce operational costs

4. To enhance digestion rate

The correct answer is: To prevent short circuiting

Removing solids from the digester immediately before feeding it is essential for preventing short circuiting within the digestion process. Short circuiting occurs when the flow of material through the digester is too rapid, leading to insufficient contact time for the bacteria to effectively break down the organic material. If solids are allowed to accumulate and are not removed properly before feeding, they can disrupt the flow patterns within the digester, causing the influent to bypass a significant portion of the digester and resulting in incomplete digestion. Maintaining optimal flow conditions is crucial for maximizing the efficiency of the digestion process. When solids accumulation is managed correctly, it ensures that the active biological processes continue uninterrupted, allowing for better conversion of organic materials into biogas. Therefore, addressing the solids removal ensures the digester operates at its full potential and maintains a stable environment for the microorganisms involved in digestion.